The most refined Mazda ever produced, but don't expect high levels of performance.

Q&A With Dave Coleman - Mazda Engineering

SAVAGEGEESE: Exhaust Manifold with integrated flaps/butterflies (bolted to head before turbo): Are they pressure actuated or electronically actuated to open and how does this work?DAVE COLEMAN:These parts are electrically actuated.

SAVAGEGEESE: The same manifold with butterflies, can this individual part be replaced due to failure/carbon buildup or do you have to replace the entire exhaust manifold assembly?

DAVE COLEMAN: The manifold is an individual part bolted between the turbo and cylinder head and it can be replaced separately. That said, this part is already a very mature part, having been redesigned several times during development after extensive durability testing. The main challenge is coping with the extreme temperature swings seen in the exhaust stream. To handle this environment, the three butterflies are on one shaft that only contacts the manifold at two points to avoid the binding as parts warp during periods of uneven heating. The shaft is also a made from an extremely temperature stable inconel super alloy originally designed for jet engines. Carbon buildup in the exhaust is not really an issue with the level of combustion control in modern engines.

SAVAGEGEESE: Steering Calibration: Seems heavy and well suited to vehicle’s weight compared to competition that use light/fast steering as a trick to hide weight/body control, how is the steering calibrated vs. other Mazda vehicles?

DAVE COLEMAN:All our cars are tuned with the same goals of Jinba Ittai, which is a deeply intuitive interaction between the car and driver. Steering feedback is an essential part of this, but it isn't just making it heavy, it's making sure the effort accurately communicates what the car is doing, and making sure the car's responses are fluid, linear, and precisely linked to the driver's inputs. These basic goals don't change from car to car - just the details do.

SAVAGEGEESE: Diff Upgrades: The On demand system was up scaled, how much larger in percentage in size and weight were components such as diff, driveshaft. (25% larger etc.)?DAVE COLEMAN:There is very little difference between the CX-5 and CX-9 AWD systems. These parts were designed at a platform level, and this CX-9 load was planned from the beginning. So essentially, CX-5 has had CX-9 parts in it since the beginning. The CX-3, being on a smaller platform, has a smaller diff and torque coupling.

SAVAGEGEESE: Was transmission upgraded from the CX-5 and what is different?

DAVE COLEMAN:The transmission is the same high-torque design used in our diesel models globally. It is similar in basic design to the CX-5 transmission, but with larger shafts, gears and clutch packs as needed. This transmission has been in use globally for several years already.

SAVAGEGEESE: Was there a need for oil cooling or transmission cooling on CX-9 and how do you do oil temperature management and did you have to develop a different 5w30 oil for your turbo application?

DAVE COLEMAN:There is an oil/water heat exchanger added for the engine oil. The diff has a small cooler. Generally, SKYACTIV transmissions don't need coolers because they run with the torque converter locked. Torque converter slippage is the main source of heat in ATs.

SAVAGEGEESE: How is carbon build up managed and additional blow created from turbo associated with DI?

DAVE COLEMAN:Carbon buildup on DI intake valves has two contributors. The oil itself getting on the valves, and the valves being at a temperature that promotes the formation of hard deposits.

We've dramatically reduced the oil in the intake stream compared to our last DI Turbo through several measures. First, oil blowing past turbo seals directly into the intake stream has been reduced with better turbo oil seals and lower oil pressure in the turbo itself. Actual blow-by has been reduced across the board with SKYACTIV engines by improving the roundness of the cylinder bores through improved analysis of casting, machining and assembly stresses that can slightly warp the bores. Taking this into account in the design process has given us much better blow-by performance.

Finally, the realization of the sensitivity to intake valve temperature has allowed us to design the cylinder head structure, cooling system and calibration to manage intake valve temperatures to prevent carbon buildup.

SAVAGEGEESE: So it makes sense that this motor won’t appear in this generation, CX-5, Mazda3 and Mazda6, however in regards to the engine design, with the way the head was designed on the exhaust side and the tuning this does not seem like setup that could be easily retuned or adapted for more linear tq and power delivery on car platforms, what is the thought process here and/or are there different iterations of the 2.5T or a 2.0T for cars in the works?